1. Technical Field
This invention relates generally to networks, such as Infiniband networks, and more particularly to failover of nodes within such networks.
2. Description of the Prior Art
Input/output (I/O) networks, such as system buses, can be used for the processor of a computer to communicate with peripherals such as network adapters. However, constraints in the architectures of common I/O networks, such as the Peripheral Component Interface (PCI) bus, limit the overall performance of computers. Therefore, new types of I/O networks have been proposed.
One new type of I/O network is known and referred to as the InfiniBand network. The InfiniBand network replaces the PCI or other bus currently found in computers with a packet-switched network, complete with one or more routers. A host channel adapter (HCA) couples the processor to a subnet, whereas target channel adapters (TCAs) couple the peripherals to the subnet. The subnet includes at least one switch, and links that connect the HCA and the TCAs to the switches. For example, a simple InfiniBand network may have one switch, to which the HCA and the TCAs connect through links. Topologies that are more complex are also possible and contemplated.
Each end node of an Infiniband network contains one or more channel adapters (CAs) and each CA contains one or more ports. Each port has a local identifier (LID) assigned by a local subnet manager (SM). Within the subnet, LIDs are unique. Switches use the LIDs to route packets within the subnet. Each packet of data contains a source LID (SLID) that identifies the port that injected the packet into the subnet and a destination LID (DLID) that identifies the port where the Infiniband fabric, or network, is to deliver the packet.
The Infiniband network methodology provides for multiple virtual ports within a physical port by defining a LID mask count (LMC). The LMC specifies the number of least significant bits of the LID that a physical port masks, or ignores, when validating that a packet DLID matches its assigned LID. Switches do not ignore these bits, however. The SM can therefore program different paths through the Infiniband fabric based on the least significant bits. The port thus appears to be 2LMC ports for the purpose of routing across the fabric.
For critical applications needing round-the-clock availability without failure, failover of individual applications and thus communication endpoints, or end nodes, is usually required. Communication endpoints in the context of an Infiniband network are associated with CA ports. The applications use the endpoints to communicate over the Infiniband network, such as with other applications and so on. Transparent failover of an endpoint can mean that another endpoint takes over the responsibilities of the failed endpoint, in a manner that does not disrupt communications within network itself.
Transparent failover of endpoints and other nodes within an Infiniband network, however, is difficult to achieve because of how the endpoints are addressed. Failover requires that the LID be reassigned to a new port that is taking over for the failed port. However, the new port usually already has a LID assigned to it. Therefore, the only way an additional LID can be assigned is to expand the LMC range on the port, and then to ensure that the new LID falls within that range.
Expanding LMC ranges on ports is difficult in practice, however, and requires sometimes significant overhead to ensure that takeover ports can have the LIDs of failed ports assigned to them. LID failover is therefore viewed as a problem and a barrier to the successful rollout of Infiniband networks where transparent failover is required. For these reasons, as well as other reasons, there is a need for the present invention.